mysqldnd
is a library that provides MySQL-connectivity to mysql_*
, mysqli_*
and PDO functions/methods.
Those three extensions are compiled either with mysqlnd
, or with libmysql
; and cannot be compiled using both at the same time : they use one library, or the other.
This means the only way to switch between libmysql
and mysqlnd
is to re-compile PHP (or, at least, the mysqli extension, in your case) ; or to install a version of it that is compiled against the library you want.
Basically, this can only be done by the administrator of your server -- so, in your case, you seem to be stuck with libmysql
; even if it lacks some interesting features.
Once again, using an hosting service with which you are not administrator has advantages (less maintenance for you, you probably pay less), but you are not able to do whatever you want with "your" server.